China’s recent declaration of an Air Defense Identification Zone (ADIZ) in the East China Sea has stimulated much debate and concern and interpretations have varied widely. The Chinese government has asserted that the ADIZ is in accordance with international practice and will contribute to regional peace and air security. But the announcement drew protests from Japan, the United States, South Korea, Australia and others. Within days, military aircraft from the United States, Japan and South Korea defied China’s assertion that all aircraft entering the ADIZ would have to submit flight plans, maintain radio contact and follow directions from the Chinese Defense Ministry or face “emergency defensive measures.”